Regenerative Braking Energy Calculator
Work out how much energy braking releases and how much of it a car can put back in the battery.
Results
The dashed line marks the value you entered.
What this tool does
Slowing a car down destroys kinetic energy, and kinetic energy goes as the square of speed — which is why braking from 100 km/h releases four times as much as braking from 50. Coming down a hill adds potential energy on top. A regenerative system catches part of that on the way back to the battery, but never all of it: the motor, the inverter and the battery each take a cut, and a hard stop outruns what the motor can absorb so the friction brakes take the rest. The share you recover is the one number here that is yours to set.
Formula
energy = ½ × mass × (speed before² − speed after²) + mass × g × height , recovered = energy × share
Variables
| Symbol | Meaning | Unit |
|---|---|---|
m | Mass | kg |
v1 | Speed before braking | km/h |
v2 | Speed after braking | km/h |
h | Height lost on the slope | m |
eff | Share of braking energy recovered | % |
cons | Consumption | Wh/km |
RE | Energy sent back to the battery | Wh |
BE | Energy released by braking | kJ |
KE | Kinetic energy | kJ |
RK | Extra range it buys back | km |
Worked example
- Mass1800 kg
- Speed before braking100 km/h
- Speed after braking0 km/h
- Height lost on the slope0 m
- Share of braking energy recovered70 %
- Consumption180 Wh/km
- Energy sent back to the battery135.0 Wh
- Energy released by braking694.4 kJ
- Kinetic energy694.4 kJ
- Extra range it buys back0.75 km
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- Mixing units is the most common source of error. Convert every input to the units shown next to each field before calculating.
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.